The economic disposal of waste solids and recovery of clean water from aqueous solutions and dispersions thereof is a recognized problem. Also, the need to recover clean water and valuable solid materials from aqueous solutions and dispersions thereof is a common occurrence. Ideally, apparatuses and processes for the recovery of water from aqueous solids should provide ease of disposition of all constituents, avoidance of pollution, economic operation and hygienic handling, and should, in addition, yield clean water. Furthermore, in the course of recovering clean water it is desirable to obtain by-products, both solid and liquid, which are either valuable in themselves or can be utilized to further the economics of the process. For purposes of this invention it is to be understood that the term "aqueous solids" is employed generically to include suspensions, dispersions, solutions, mixtures and other forms of fluid association of solids in water.
In our U.S. Pat. No. 3,855,079 titled "Process and Apparatus for Recovering Residual Oil from Solids Dehydrated in an Oil Medium and Grossly Deoiled" are described process and apparatus whereby aqueous solids are admixed with a relatively non-volatile fluidizing oil to form a mixture which is dehydrated by heat evaporation. The substantially anhydrous solids in fluidizing oil slurry thus formed is thereafter separated into the oil phase and the solids phase. However, the solids have sorbed thereon appreciable amounts of fluidizing oil which contaminates the solids and which will be lost to the process and contribute to unfavorable economics if not recovered. Accordingly, the fluidizing oil-laden solids are subjected to a subsequent extraction step using a relatively volatile, water-immiscible light oil. The light oil-laden solids are then brought into direct contact with blowing steam. The presence of the blowing steam reduces the boiling point of the residual water-immiscible light oil to effect is more efficient removal from the solids.